just finished (almost) my new spoilboard for my 7x12, and I thought i'd share. I'll post up the parts / gcode so if anyone wants to cut/build one, they can.
3/4" MDF sheet, 17" x 8" (19mm thick)
20 T-Nuts, I used 1/4-20 x 9/16 (Got mine at Lowes, but Home Depot sells these too. Height is not critical.
1/8" endmill, with at least 1" cut depth. I used a 2 flute one that works well on wood.
10 No. 4 x 1" Socket Head Sheet Metal Screws (Du-bro). I like the socket head screws. Hobby stores sell these (Great Hobbies in Canada)
10 M3 Washers (Hobby store again, hard to find these tiny washers)
hammer for setting t-nuts
a pair of bolt/screws for screwing down MDF to old spoilboard
1. Bolt/attach the MDF to your old spoilboard. I lined the front of the MDF up with the front of the old spoilboard, just to keep things neat.
2. Mark the MDF so you know where the middle is. Touch off to the middle of the new spoilboard, Z should be touched off to the TOP of the MDF.
3. Run the cutfile for the bottom of the spoilboard.
4. Remove the spoilboard, apply epoxy to countersink area, insert t-nuts, and hammer the t-nuts in place. I did 5 at a time so the epoxy didn't harden in the middle of the job. Make sure they sit flush with the MDF.
5. Reattach the MDF to the old spoilboard, but with the uncut face up (T-Nuts down).
6. Touch off to the middle of the spoilboard again, Z touchoff at the top of the MDF
7. Run the cutfile for the top of the spoilboard.
Remove new spoilboard, remove old spoilboard, screw down new spoilboard using 1" screws + washers instead of 3/4" screws. I used M3 washers for the new screws.
I'll tweak the cut file for the top a bit (to do peck drilling on the through holes), but other than that, they're good to go.
NOTE: Most of the t-nut screw-down holes have no issues, but the ones farthest from the center on the X axis MIGHT run into the side of the machine from underneath if you use bolts that are too long. None of the other t-nut clamp holes have this issue. Don't use bolts that extend past the bottom of the spoilboard on these clamp holes!
I'll post up the G-Code tomorrow.
TOP (attach to CNC holes): The holes are 100mm apart on the Y axis, and 80mm apart on the X axis. The countersink is 6mm deep, and 8mm wide. Through hole is 1/8" wide.
BOTTOM (clamp stuff down holes): The holes are 90mm apart on the X axis, and 30mm apart on the Y axis. The countersink is 2mm deep, and XXmm wide (I forget right now, I'll have to check). Through hole is XXmm wide (Have to check this too).
Last edited by jblakey
on Wed Feb 25, 2015 10:23 am, edited 4 times in total.